linux-kernel - Re: How to increase maximum user cpu usage allowed on a multi core system?

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Date:	Tue, 17 Mar 2015 19:34:08 +0100
From:	poma <pomidorabelisima@...il.com>
To:	Borislav Petkov <bp@...e.de>
CC:	Community support for Fedora users 
	<users@...ts.fedoraproject.org>,
	stan <stanl-fedorauser@...mail.net>,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: How to increase maximum user cpu usage allowed on a multi core
 system?

On 09.03.2015 20:03, stan wrote:
> I'm running Fedora 21 with a custom compiled kernel,
> 3.19.0-1.20150211.fc21.x86_64.
> 
> I have a multi core system with 6 cores.  All are recognized by the
> kernel.  
> 
> But, when I run a compile job with -j6, in order to allow all six cores
> to be used, it limits the total amount of usage to 100% of a *single*
> core.  So, it might use all six cores, but the sum of the percentages
> on those six cores is always around 100% of one core.  This is from
> htop output.
> 
> On large compilations, like the kernel or firefox, even using 4 cores
> could drastically reduce compile time.
> 
> I've looked at /etc/security/limits.conf, but it doesn't seem to have a
> setting for this.  I've also looked at the /proc system to see if there
> is a kernel variable, though that seems unlikely, with no luck.  Online
> searching found ways to limit the amount that a single job can get, but
> not how to set this for a user.  There must be a configuration variable
> somewhere that is limiting the amount of total cpu a user can use.  But
> I can't find it.
> 
> Can anyone help?
> 


Borislav, can you help explain the man why this is happening with his Piledriver.
http://www.cpu-world.com/CPUs/Bulldozer/AMD-FX-Series%20FX-6300.html


poma


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